Xamarin 的 RadioBox 列表从视图模型中设置 GroupName

Question

All the examples for RadioButtons I've found so far have the values hard-coded in the xaml for the page. I'm looking to feed a list of strings (for now) from a database and running into an issue with the GroupName.

My data template for a radio display type:

            <DataTemplate x:Key="RadioTemplate">
                <StackLayout>
                    <Label 
                        Text="{Binding Name}"
                        Style="{StaticResource LabelStyle}">
                    </Label>
                    <ListView ItemsSource="{Binding Choices.Choices}">
                        <ListView.ItemTemplate>
                            <DataTemplate>
                                <ViewCell>
                                    <RadioButton Value="{Binding}"
                                            Content="{Binding}"
                                            GroupName="someGroupName"
                                            CheckedChanged="OnRadioChanged">
                                    </RadioButton>
                                </ViewCell>
                            </DataTemplate>
                        </ListView.ItemTemplate>
                    </ListView>
                </StackLayout>
            </DataTemplate>


MainPageViewModel.cs
using System;
using System.Collections.ObjectModel;
using System.Windows.Input;
using Xamarin.Forms;
using FieldDataTemplateSelectorSample.Validations;

namespace FieldDataTemplateSelectorSample
{
    public class MainPageViewModel : ValidationViewModelBase
    {
        public MainPageViewModel()
        {
            _fields = new ObservableCollection<FieldViewModel>();
        }

        private ObservableCollection<FieldViewModel> _fields;
        public ObservableCollection<FieldViewModel> Fields
        {
            get { return _fields; }
            set
            {
                _fields = value;
                RaisePropertyChanged();
            }
        }

        private bool _showValidationSummary;
        public bool ShowValidationSummary
        {
            get { return _showValidationSummary; }
            set
            {
                _showValidationSummary = value;
                RaisePropertyChanged();
            }
        }

        ICommand _submitCommand;
        public ICommand SubmitCommand
        {
            get => _submitCommand ?? (_submitCommand = new Command(ValidateAndSave));
        }

        private void ValidateAndSave(object obj)
        {
            ValidateAll();
            if (ErrorStateManager.HasError)
            {
                ShowValidationSummary = true;
            }
            else
            {
                ShowValidationSummary = false;
            }
        }
    }
}

using System.Collections.Generic;
using Xamarin.Forms;
using FieldDataTemplateSelectorSample.Validations;


namespace FieldDataTemplateSelectorSample
{
    public class FieldViewModel : ValidationViewModelBase
    {
        public FieldViewModel()
        {
            _choices = new ChoiceViewModel();
        }

        private string _value;

        public long Id { get; set; }
        public string Name { get; set; }
        public string Title { get; set; }
        public string Code { get; set; }
        public string Value 
        { 
            get
            {
                return _value;
            }           
            set
            {
                _value = value;
                RaisePropertyChanged();
                Validate();
            }
        }
        public string PlaceholderText { get; set; }
        public int SortOrder { get; set; }
        public string DisplayType { get; set; }
        public bool IsReadOnly { get; set; }
        public bool IsEnabled { get; set; }

        private ChoiceViewModel _choices;
        public ChoiceViewModel Choices
        {
            get 
            { 
                return _choices; 
            }
            set 
            { 
                _choices = value; 
                RaisePropertyChanged(); 
            }
        }

        void OnChoicesRadioButtonCheckedChanged(object sender, CheckedChangedEventArgs e)
        {
            // what else do we need to do?  Update value?
            
            RaisePropertyChanged();
        }
    }
}

using System;
using System.Collections.Generic;
using System.Text;

namespace FieldDataTemplateSelectorSample
{
    public class ChoiceViewModel
    {
        public ChoiceViewModel()
        {
            Choices = new List<string>();
        }

        public string Code { get; set; }
        public List<string> Choices { get; set; }
    }
}

As long as I hard-code the GroupName for the RadioButton in the ViewCell, everything works but that I'll end up with one group name for every single radio button on the page. I've tried adding the property to the StackLayout in the template:

<StackLayout RadioButtonGroup.GroupName="someGroup">

and taking it out out of the RadioButton but when I put a breakpoint in OnRadioChanged, the GroupName comes in as null.

I'd like to use the Code property in the ChoiceViewModel as the group name but haven't gotten the relative binding correct yet. Any help with the binding or different way to do the DataTemplate is appreciated.

Answer 1

you could use a bindable StackLayout which will give you more control over the containter

<StackLayout>
    <Label Text="{Binding Name}" Style="{StaticResource LabelStyle}" />
    <StackLayout RadioButtonGroup.GroupName="{Binding Name}"      
           BindableLayout.ItemsSource="{Binding Choices.Choices}" >
       <BindableLayout.ItemTemplate>
         <DataTemplate>
           <ViewCell>
               <RadioButton Value="{Binding}" Content="{Binding}"
                   CheckedChanged="OnRadioChanged" />
           </ViewCell>
         </DataTemplate>
      </BindableLayout.ItemTemplate>
  </StackLayout>
</StackLayout>